Fabrication of highly porous scaffold materials based on functionalized oligolactides and preliminary results on their use in bone tissue engineering

Evaluation of Cell Adhesion and Proliferation on a Novel Tissue Engineering Scaffold Containing Chitosan and Hydroxyapatite

Porous chitosan-hxdroxyapatite hybrids were developed by partial enzymatic degradation [14] of the chitin/chitosan surface using chitosanase and lysozyme. This article evaluates the influence of chitosan and hydroxyapatite components, substrate roughness, stability, as well as surface porosity produced by enzymatic hydrolysis to cell adhesion and proliferation. L929 mouse fibroblastic lung cells were cultured on enzymatic degraded porous chitosan-hydroxyapatite hybrids. The presence of hydroxyapatite and porosity produced by partial lysozyme hydrolysis enhance cell proliferation. Besides, cell adhesion and proliferation are primarily dependent on substrate roughness and stability.

Ex vivo bio-compatibility of honey-alginate fibrous matrix for HaCaT and 3T3 with prime molecular expressions

Honey's inherent compositional diversity, bio-compatibility and time tested therapeutic efficacy, especially in tissue repair as a topical agent, attract researchers towards harnessing its biomaterial potential particularly in developing matrix for tissue engineering applications. Hence, this study fabricates fibrous mat from optimum honey-alginate formulation and alginate solution using wet spinning technology. The physical and morphological properties of the scaffolds are assessed and finally their comparative biological performances are evaluated through in vitro studies on adherence, viability and prime molecular expression of HaCaT and 3T3 cells. The honey-alginate scaffold demonstrates better performance than that of alginate in terms of cellular adherence, viability and proper expression of cell-cell adhesion molecule (E-cadherin) and prime molecules of extra cellular matrix (Collagen I and III) by HaCaT and 3T3 respectively.

Potential use of porous titanium-niobium alloy in orthopedic implants: preparation and experimental study of its biocompatibility in vitro

Background

The improvement of bone ingrowth into prosthesis and enhancement of the combination of the range between the bone and prosthesis are important for long-term stability of artificial joints. They are the focus of research on uncemented artificial joints. Porous materials can be of potential use to solve these problems.

Objectives/Purposes

This research aims to observe the characteristics of the new porous Ti-25Nb alloy and its biocompatibility in vitro, and to provide basic experimental evidence for the development of new porous prostheses or bone implants for bone tissue regeneration.

Methods

The Ti-25Nb alloys with different porosities were fabricated using powder metallurgy. The alloys were then evaluated based on several characteristics, such as mechanical properties, purity, pore size, and porosity. To evaluate biocompatibility, the specimens were subjected to methylthiazol tetrazolium (MTT) colorimetric assay, cell adhesion and proliferation assay using acridine staining, scanning electron microscopy, and detection of inflammation factor interleukin-6 (IL-6).

Results

The porous Ti-25Nb alloy with interconnected pores had a pore size of 200 µm to 500 µm, which was favorable for bone ingrowth. The compressive strength of the alloy was similar to that of cortical bone, while with the elastic modulus closer to cancellous bone. MTT assay showed that the alloy had no adverse reaction to rabbit bone marrow mesenchymal stem cells, with a toxicity level of 0 to 1. Cell adhesion and proliferation experiments showed excellent cell growth on the surface and inside the pores of the alloy. According to the IL-6 levels, the alloy did not cause any obvious inflammatory response.

Conclusion

All porous Ti-25Nb alloys showed good biocompatibility regardless of the percentage of porosity. The basic requirement of clinical orthopedic implants was satisfied, which made the alloy a good prospect for biomedical application. The alloy with 70% porosity had the optimum mechanical properties, as well as suitable pore size and porosity, which allowed more bone ingrowth.

Engineering bone tissue using human dental pulp stem cells and an osteogenic collagen-hydroxyapatite-poly (L-lactide-co-ε-caprolactone) scaffold

The aim of this study was to design a new natural/synthetic bioactive bone scaffold for potential use in bone replacement applications. We developed a tri-component osteogenic composite scaffold made of collagen (Coll), hydroxyapatite (HA) and poly(l-lactide-co-ε-caprolactone) (PLCL). This Coll/HA/PLCL composite scaffold was combined with human osteoblast-like cells obtained by differentiation of dental pulp stem cells (DPSCs) to engineer bone tissue in vitro. Results show that the 3D Coll/HA/PLCL composite scaffold was highly porous, thereby enabling osteoblast-like cell adhesion and growth. Cultured in the Coll/HA/PLCL scaffold, the osteoblast-like cells expressed different osteogenic genes, produced alkaline phosphatase and formed nodules more than did PLCL alone. Micro-CT analyses revealed a significant (30%) increase of tissue mineralisation on the surface as well as inside of the Coll/HA/PLCL scaffold, thus confirming its effectiveness as a bone regeneration platform.

In vitro degradation and drug release of a biodegradable tissue adhesive based on functionalized 1,2-ethylene glycol bis(dilactic acid) and chitosan

Biodegradability and adhesive-associated local drug release are important aspects of research in tissue adhesive development. Therefore, this study focuses on investigating the in vitro degradation and drug release of a tissue adhesive consisting of hexamethylene diisocyanate functionalized 1,2-ethylene glycol bis(dilactic acid) and chitosan chloride. To prevent infections, ciprofloxacin hydrochloride (CPX·HCl) was incorporated into the adhesive. The influence of CPX·HCl on the adhesive reaction and adhesive strength was analyzed by FTIR-ATR-spectroscopy and tensile tests. The CPX·HCl release was investigated by HPLC. The degradation-induced changes at 37 °C were evaluated by gravimetric/morphological analyzes and micro-computer tomography. The antibiotic potential of the CPX·HCl loaded adhesive was determined by agar diffusion tests. The degradation tests revealed a mass loss of about 78 % after 52 weeks. The adhesive reaction velocity and tensile strength were not influenced by CPX·HCl. Using a 2 mg/g CPX·HCl loaded adhesive an inhibition of all tested bacteria was observed.

Hydroxyapatite/gelatin/gellan sponges as nanocomposite scaffolds for bone reconstruction

The aim of this work was the morphological, physicochemical, mechanical and biological characterization of a new composite system, based on gelatin, gellan and hydroxyapatite, and mimicking the composition of natural bone. Porous scaffolds were prepared by freeze-drying technique, under three different conditions of freezing. The morphological analysis showed a homogeneous porosity, with well interconnected pores, for the sample which underwent a more rapid freezing. The elastic modulus of the same sample was close to that of the natural bone. The presence of interactions among the components was demonstrated through the physicochemical investigation. In addition, the infrared chemical imaging analysis pointed out the similarity among the composite scaffold and the natural bone, in terms of chemical composition, homogeneity, molecular interactions and structural conformation. Preliminary biological characterization showed a good adhesion and proliferation of human mesenchymal stem cells.

Human adipose-derived stem cells (hASCs) proliferate and differentiate in osteoblast-like cells on trabecular titanium scaffolds

The use of stem cells in regenerative medicine is an appealing area of research that has received a great deal of interest in recent years. The population called human adipose tissue-derived stem cells (hASCs) share many of the characteristic of its counterpart of marrow including extensive proliferative potential and the ability to undergo multilineage differentiation along classical mesenchymal lineages: adipogenesis, chondrogenesis, osteogenesis, and myogenesis. The aim of this study was to evaluate with biochemical and morphological methods the adhesion and differentiation of hASCs grown on trabecular titanium scaffolds. The hASCs isolated from subcutaneous adipose tissue after digestion with collagenase were seeded on monolayer and on trabecular titanium scaffolds and incubated at 37 degrees C in 5% CO(2) with osteogenic medium or control medium.The results showed that hASCs were able to adhere to titanium scaffolds, to proliferate, to acquire an osteoblastic-like phenotype, and to produce a calcified extracellular matrix with protein, such as, decorin, fibronectin, osteocalcin, osteonectin, osteopontin, and type I collagen. These data suggest that this kind of scaffold/cells construct is effective to regenerate damaged tissue and to restore the function of bone tissue.

Activity-dependent neuronal cell migration induced by electrical stimulation

Recently, we found that electrical stimulation can induce neuronal migration in neural networks cultured for more than 3 weeks on microelectrode arrays. Immunocytochemistry data showed that the aggregation of neurons was related to the emergence of astrocytes in culture. In this study, when neurons were cocultured with astrocytes, electrical stimulation could induce the migration of neuronal cell bodies after only 1 week in culture, while the same stimulation paradigm caused neural necrosis in neuron-only cultures. In addition, the stimulation-induced migration was inhibited by blocking action potentials in neural networks using the voltage-gated sodium channel blocker, tetrodotoxin. Immunocytochemistry was performed to monitor precisely the neuronal migration and count the number of neurons. These results indicate that neuronal migration of cell bodies is dependent on neuronal activity evoked by electrical stimulation and can be enhanced by coculturing with astrocytes. We believe this method can be employed as a means for modifying neural networks and improving the interface between electrodes and neurons.

Degradable phosphate glass fiber reinforced polymer matrices: mechanical properties and cell response

The development of biodegradable materials for internal fracture fixation is of great interest, as they would both eliminate the problem of stress shielding and obviate the need for a second operation to remove fixation devices. Preliminary investigations for the production of degradable fiber reinforced polymer composite materials are detailed. Composites were produced of phosphate invert glass fibers of the glass system P(2)O(5)-CaO-MgO-Na(2)O-TiO(2), which showed a low solubility in previous work. The fibers were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide. Fracture behavior, bending strength and elastic modulus were evaluated during 3-point bending tests and the fracture surface of the composites was investigated using a scanning electron microscope. Short-term biocompatibility was tested in an FDA/EtBr viability assay using MC3T3-E1 murine pre-osteoblast cells and showed a good cell compatibility of the composite materials. Results suggested that these composite materials are biocompatible and show mechanical properties which are of interest for the production of degradable bone fixation devices.

Development of a new calcium phosphate powder-binder system for the 3D printing of patient specific implants

A key requirement for three-dimensional printing (3-DP) of medical implants is the availability of printable and biocompatible powder-binder systems. In this study we developed a powder mixture comprising tetracalcium phosphate (TTCP) as reactive component and beta-tricalcium phosphate (beta-TCP) or calcium sulfate as biodegradable fillers, which can be printed with an aqueous citric acid solution. The potential of this material combination was demonstrated printing various devices with intersecting channels and filigree structures. Two post-processing procedures, a sintering and a polymer infiltration process were established to substantially improve the mechanical properties of the printed devices. Preliminary examinations on relevant application properties including in vitro cytocompatibility testing indicate that the new powder-binder system represents an efficient approach to patient specific ceramic bone substitutes and scaffolds for bone tissue engineering.

Nanocomposites based on poly-D,L-lactide and multiwall carbon nanotubes

A possibility of poly-D,L-lactide modification by multiwall carbon nanotubes (MWCNT) has been shown. MWCNT were prepared from methane-air mixture upon atmospheric pressure without catalyst on high voltage atmospheric pressure discharge plasma set-up. According to scanning and transmission electronic microscope data carbon nanotubes diameters were within 12-60 nm. Quantities of MWCNT incorporated did not exceed 0.5%. Nanocomposites were obtained by sonification of mixture of a poly-D,L-lactide solution in chloroform and MWCNT followed by film casting on glass substrates. Tensile strength and thermomechanical properties of the dried composite films were investigated. Introduction of MWCNT into poly-D,L-lactide has been shown to cause the enhanced polymer stability to thermal oxidative destruction. Taking into account the results obtained one could anticipate that implants from nanocomposites of poly-D,L-lactide with MWCNT would be dispersed in a living organism more slowly as compared to implants from pure poly-D,L-lactide without additives.

Fabrication andin vitro characterization of porous biodegradable composites based on phosphate glasses and oligolactide-containing polymer networks

Degradable porous composite materials for use as temporary bone replacement or tissue engineering scaffolds were produced using a methacrylate-modified oligolactide polymer network and phosphate invert glasses in the system P2O5-CaO-MgO-Na2O-(TiO2). Porous glasses with an open interconnective porosity were produced by a salt sintering process. Compressive strengths were significantly enhanced by polymer coating of the inner surface of the porous glasses or by fabrication of glass powder-reinforced porous polymer specimens. In vitro degradation in simulated body fluid showed a degradation pattern of the composites which could be modulated by the composition and resulting solubility of the incorporated glass phase. Cytocompatibility of the composites was investigated in a FDA/EtBr viability assay using an MC3T3-E1 osteoblast-like cell line and showed good biocompatibility of the materials in vitro.